The prior art includes the use of a rotary drive system of the type comprising:                a direct voltage source,        an electric motor having an axis of rotation, and comprising independent phases having directions about the axis of rotation,        an inverter for connecting each phase to the direct voltage source, and        a control device for supplying a command to the inverter.        
In some drive systems, the control device is intended to control the inverter so as to obtain a zero homopolar current in the electric motor, so as to meet some objectives, whereas in other drive systems, the control device is intended to control the inverter so as to obtain a non-zero homopolar current in the electric motor, so as to meet other objectives.
It may be sought to have a drive system suitable for meeting a plurality of objectives during the operation thereof.